Results of current therapy of most malignant adult brain tumors remain disappointing. Despite the most aggressive multimodality treatment, median survival in the most common tumor, glioblastoma multiforme, is 10 months and cure is anecdotal. These tumors extend beyond the limits of surgical resection and total dose of conventional external beam radiotherapy is limited by surrounding normal brain tolerance. By placing radioactive seeds of I 125 directly into the tumor bed we hope to achieve: 1) a high radiation dose to the tumor; 2) a low radiation dose to surrounding normal brain; and 3) increased therapeutic ratio with radiation delivered at low dose rates.